Merge pull request #20705 from hvitved/rust/type-inference-unit

Rust: Infer more `()` types

rust/ql/.generated.list

@@ -135,7 +135,7 @@ lib/codeql/rust/elements/RefPat.qll fe076bdccb454111b38f360837d180274ba8a003b4cf
 lib/codeql/rust/elements/RefTypeRepr.qll 563d2edc097aa1896b3dea5a3918e6225f23dda91b3fb46e2f4c32feb813d56c af3bd746239130e3e94dd41ab682473b29b8b900b05c557beb8a2eba6508ebd9
 lib/codeql/rust/elements/Rename.qll 5cb0ebad580d9842cfe65033059d4d373a1386f047f3a78f402a93e060e2c13e 642c6f37d94442575df12b2e998572a725d094ac5ae76147a56057e75138d72b
 lib/codeql/rust/elements/RestPat.qll 5fedfac18080b068f597c9bbb84de672834f72cc22295d6312e111f151f8e3c7 c0e1f77bfcdd40e8ab06ad8c138e6098d79940247758adf9de03a05b00c23de3
-lib/codeql/rust/elements/RetTypeRepr.qll a603393d373f38831dded00878c3299d61fdb977723d3e1038692f7a46bfebc5 583c626f7ae7fb4ec9a9f93f072330c16560ab52c8dfec566c46af40fb9f39f8
+lib/codeql/rust/elements/RetTypeRepr.qll d68b7c6c2eda13821fcfe085ac3d63010d89a206be09d23deaf531cac405ba96 6db787a96d95265ca20a17ce00603a678b39ac8c7c1d0e1ad6ed119dcf9858fa
 lib/codeql/rust/elements/ReturnExpr.qll b87187cff55bc33c8c18558c9b88617179183d1341b322c1cab35ba07167bbdb 892f3a9df2187e745c869e67f33c228ee42754bc9e4f8f4c1718472eb8f8c80f
 lib/codeql/rust/elements/ReturnTypeSyntax.qll f30b779f79bc2f0329d5585a462511e1aaa9da63182cb45231873a9bd9644d19 5ba004dae2bca323ced27bb4b2f54f725ae974421ab11b176eac4888c642b3fa
 lib/codeql/rust/elements/SelfParam.qll e36b54cdc57529935910b321c336783e9e2662c762f3cd6af492d819373ff188 7a4735dbf532fc0c33ebdb0b5c1dfc4e5267e79ceff4ca8977065eb0ce54aaf5
@@ -177,7 +177,7 @@ lib/codeql/rust/elements/Unimplemented.qll bf624d28163e5c99accda16c0c99f938bec4a
 lib/codeql/rust/elements/Union.qll 13f7f62e98b117d18e79db5f6e6535447bc069ebb08f7cdb390b012678b7e085 bd8c37bc0ff09926753bc250e1848ed25923f224829d0136afc27b749eaddd1f
 lib/codeql/rust/elements/Use.qll fdcf70574403c2f219353211b6930f2f9bc79f41c2594e07548de5a8c6cbb24d e41f2b689fcbeb7b84c7ba8d09592f7561626559318642b73574bbac83f74546
 lib/codeql/rust/elements/UseBoundGenericArg.qll f16903f8fff676d3700eaad5490804624391141472ecc3166ccb1f70c794c120 5efda98088d096b42f53ceccae78c05f15c6953525b514d849681cb2cf65b147
-lib/codeql/rust/elements/UseBoundGenericArgs.qll d9821a82a1d57e609fdc5e79d65e9a88b0088f51d03927e09f41b6931d3484ab 181483a95e22622c7cee07cce87e9476053f824a82e67e2bdecabf5a39f672ad
+lib/codeql/rust/elements/UseBoundGenericArgs.qll 841913cfbb84de14aab1820a5433eae978bbadbb8e6d413b8ba70780c7328335 c9ec9d086cff91d15c3aea64f1080b22b41cdaf64e3c8b192aaaec17604a5d10
 lib/codeql/rust/elements/UseTree.qll e67c148f63668319c37914a46ff600692de477242a0129fa1bb9839754c0f830 de9b39d3d078d51ec9130db6579bff13e6297e60556a7214a5c51cbf89d92791
 lib/codeql/rust/elements/UseTreeList.qll 92ebfee4392a485b38fb3265fdede7c8f2ed1dbe2ab860aa61b1497c33874d25 a4e677455d20838e422e430eebd73d0a488e34e8c960f375fef7b99e79d4c911
 lib/codeql/rust/elements/Variant.qll 7895461fa728f6c3a7293799c5e6b965b413b679566dcbd40bbe2609db8b6cde b0413547365a301bd9fbb6b266757f956394abad0a77f0e424446e23ec7d83e9
@@ -369,7 +369,7 @@ lib/codeql/rust/elements/internal/RenameConstructor.qll 65fa2e938978d154701e6cac
 lib/codeql/rust/elements/internal/RenameImpl.qll 61c681055f1f86402af0772539f702e9e19a123f8cfcfca225535c3a1a4cb1d7 1aa1c78616c4b54a31c8af74de141aef9e5ada53f3859df631ecb4238faabdbf
 lib/codeql/rust/elements/internal/RestPatConstructor.qll 45430925ddf08fba70ede44c7f413ddb41b3113c149b7efc276e0c2bf72507b4 25c678898d72446e7a975bb8b7f2fde51e55b59dbd42f2cca997c833b1a995f1
 lib/codeql/rust/elements/internal/RetTypeReprConstructor.qll 6dcb56c92a13f5ca2c9a8344bc05638cc611543896c578cd6ca185054f155537 3fe34953ba397dc31533bd28b48df76693e86b51c4a89c26ad4dfdbd816a0874
-lib/codeql/rust/elements/internal/RetTypeReprImpl.qll 799e55ffcf27bf6f010419e1d61ebbbf3448e37b903b0f13984d0b44d6b7a999 be774bb09d121c35f40c75d5bee08918e7a6b5fccb4fd573fc55a650466b46e0
+lib/codeql/rust/elements/internal/RetTypeReprImpl.qll 321355a9b39193e09ef7c38b807d7f3c221dce06b0cafd2e0ceccdfbb81712e4 02ea0fb17416889b400e0706eeacc0afc6b489b76158e8c26b9b77102df6bd60
 lib/codeql/rust/elements/internal/ReturnExprConstructor.qll 57be5afbe20aa8db6e63c1f2871914c19c186730ad7dccaa424038c6305730d5 4d3c4f2e9b38a4b54ff26a0032455cdcca3d35fec201b6c932072a9e31fbb4fe
 lib/codeql/rust/elements/internal/ReturnTypeSyntaxConstructor.qll 8994672e504d1674e5773157d0ad8a0dc3aad3d64ef295e7722e647e78e36c11 abe7df754721f4ff7f3e3bb22d275976b2e9a1ef51436a461fe52ebd2d29cff1
 lib/codeql/rust/elements/internal/ReturnTypeSyntaxImpl.qll 554af21b52fedfc356cb873e25c2429e6660ae62ea01be708de4342960cf4048 cdc497a3693bb162a7528b75e902c4743b0a974c6c44152f822a16107a83bee4
@@ -428,7 +428,7 @@ lib/codeql/rust/elements/internal/UnimplementedImpl.qll 06771abc088e0a8fc24032c9
 lib/codeql/rust/elements/internal/UnionConstructor.qll d650551a1b3ef29c5a770bdad626269cf539ed0c675af954bc847d2c6111f3f6 aca9064ad653a126ab4f03703e96b274587c852dc5e7ff3fea0fec4d45993f10
 lib/codeql/rust/elements/internal/UseBoundGenericArgImpl.qll 2f90bfd5e43113da1155445bef0334ab84acddef102bd62dfa2ef908717a5d09 dd2fa3c6081d79e1d96360dbdb339128cd944e7b7dc26c449c04f970ee1d7848
 lib/codeql/rust/elements/internal/UseBoundGenericArgsConstructor.qll 84d4a959d098fcd1713cb169e15b4945d846121701d2c5709b11e19202c21f2b 93113c92be9bc9f0b8530c308fe482dfeddc7dc827fc44049cecb3eab28df731
-lib/codeql/rust/elements/internal/UseBoundGenericArgsImpl.qll f5c082fc8f7d9acc3783da18e61ad2c9831b46c1855e1bde9b7af95adc289ad9 eb83520c5333b199788638ccd70ee8e96fc3f05306072f51a76fd0a643f8930f
+lib/codeql/rust/elements/internal/UseBoundGenericArgsImpl.qll 0f98d47c1e09c46dd3da66a4770181a0caae0512b362faaec997af22bb5f4ce7 1919235e50b9d2fee9bd5d407a0bc023a02dbb04b2662349fad5a8d6cfa98069
 lib/codeql/rust/elements/internal/UseConstructor.qll a4f790795e18abc29a50d6fbaa0db64cba781e3259a42cbf0468c24ac66b63e7 2fa288f073ac094a838c11f091def2c790b347b6a1b79407c11b10c73d6bff57
 lib/codeql/rust/elements/internal/UseTreeConstructor.qll 3e6e834100fcc7249f8a20f8bd9debe09b705fcf5a0e655537e71ac1c6f7956b cdbc84b8f1b009be1e4a7aaba7f5237823cea62c86b38f1794aad97e3dfcf64b
 lib/codeql/rust/elements/internal/UseTreeListConstructor.qll 973577da5d7b58eb245f108bd1ae2fecc5645f2795421dedf7687b067a233003 f41e5e3ffcb2a387e5c37f56c0b271e8dc20428b6ff4c63e1ee42fcfa4e67d0a
@@ -584,13 +584,13 @@ lib/codeql/rust/elements/internal/generated/PtrTypeRepr.qll 8d0ea4f6c7f8203340bf
 lib/codeql/rust/elements/internal/generated/PureSynthConstructors.qll e5b8e69519012bbaae29dcb82d53f7f7ecce368c0358ec27ef6180b228a0057f e5b8e69519012bbaae29dcb82d53f7f7ecce368c0358ec27ef6180b228a0057f
 lib/codeql/rust/elements/internal/generated/RangeExpr.qll 23cca03bf43535f33b22a38894f70d669787be4e4f5b8fe5c8f7b964d30e9027 18624cef6c6b679eeace2a98737e472432e0ead354cca02192b4d45330f047c9
 lib/codeql/rust/elements/internal/generated/RangePat.qll 80826a6a6868a803aa2372e31c52a03e1811a3f1f2abdb469f91ca0bfdd9ecb6 34ee1e208c1690cba505dff2c588837c0cd91e185e2a87d1fe673191962276a9
-lib/codeql/rust/elements/internal/generated/Raw.qll 3f86deef2f54093e3b4bd24237ba0d80fa94856fdcf2ba6a9812033bec6c0021 30cd773ce7a390afbdabd8a078f5f1408671eaca6fa7e213bed6196dfa872447
+lib/codeql/rust/elements/internal/generated/Raw.qll f50925f4925848cef73003adf01420566ca3efa16f491eadac62a30972ee9204 17d62252413618e1fa162c6c0b303ccfcac5f7f70cc170d739b20cc95f57035b
 lib/codeql/rust/elements/internal/generated/RefExpr.qll 7d995884e3dc1c25fc719f5d7253179344d63650e217e9ff6530285fe7a57f64 f2c3c12551deea4964b66553fb9b6423ee16fec53bd63db4796191aa60dc6c66
 lib/codeql/rust/elements/internal/generated/RefPat.qll 456ede39837463ee22a630ec7ab6c8630d3664a8ea206fcc6e4f199e92fa564c 5622062765f32930465ba6b170e986706f159f6070f48adee3c20e24e8df4e05
 lib/codeql/rust/elements/internal/generated/RefTypeRepr.qll 5b0663a6d234572fb3e467e276d019415caa95ef006438cc59b7af4e1783161e 0e27c8a8f0e323c0e4d6db01fca821bf07c0864d293cdf96fa891b10820c1e4b
 lib/codeql/rust/elements/internal/generated/Rename.qll 53dd50d35aa38cb6eb4174c94e8e23042b42bdc4f38df009489ebf707380483b db14fbce0d95b4dae3d7512f9bdee92e0dc2dffde5ba5d7458f2f5dd632876b0
 lib/codeql/rust/elements/internal/generated/RestPat.qll 369f5828bb78f2856d528679a9869f81859b375c2f831ff72f4507daaee976e3 17f24ce8aa6a27359c10a654667b7877ca7a1509509e2ab246ed26fe15ef66b4
-lib/codeql/rust/elements/internal/generated/RetTypeRepr.qll 7e782d6ca346fd4057e95a6eefe796e3fba7eef62144a0df78e2d115a7ae9ba9 d5da144e06d180673fa7ce274c5e7e2ca2db12b064df1155bc56f2f9378b58b4
+lib/codeql/rust/elements/internal/generated/RetTypeRepr.qll 853b7fd6c1f3678d0f9315ac23a99a0828a6e54148de24016a265039c7b1941c f1e140d2b113c494601143b735482869ee817c8a7d92026f6a511bc5c1420552
 lib/codeql/rust/elements/internal/generated/ReturnExpr.qll c9c05400d326cd8e0da11c3bfa524daa08b2579ecaee80e468076e5dd7911d56 e7694926727220f46a7617b6ca336767450e359c6fa3782e82b1e21d85d37268
 lib/codeql/rust/elements/internal/generated/ReturnTypeSyntax.qll 7b7692ca9fbe627afa0759050a740f0f42a8083446c1c3196084f5698fc570c3 96a735d60a3919c7c994f7b67930c9e51a3713940678d04a5fee54557d733c24
 lib/codeql/rust/elements/internal/generated/SelfParam.qll 076c583f7f34e29aaaf3319e9d64565a34c64caa5a6dfca240c0cc7800e9a14c 375afed1772d193b71980d3825c4ac438e90b295cba0baf58319d29a3a8463a0
@@ -634,7 +634,7 @@ lib/codeql/rust/elements/internal/generated/Unimplemented.qll a3eb304781991bff12
 lib/codeql/rust/elements/internal/generated/Union.qll 456504e6a32991ba17ca65f97636f4dfb86c758c7f8509aaca1b0d0432231dfe c96068edfec3e0755a7726426a10996455ee9f0f2d678af258719f1943a3063e
 lib/codeql/rust/elements/internal/generated/Use.qll cf95b5c4756b25bee74113207786e37464ffbc0fb5f776a04c651300afc53753 1fe26b3904db510184cb688cb0eeb0a8dbac7ac15e27a3b572d839743c738393
 lib/codeql/rust/elements/internal/generated/UseBoundGenericArg.qll 69162794e871291545ea04f61259b2d000671a96f7ca129f7dd9ed6e984067c4 31de9ebc0634b38e2347e0608b4ea888892f1f2732a2892464078cd8a07b4ee8
-lib/codeql/rust/elements/internal/generated/UseBoundGenericArgs.qll 2cc8ab0068b7bf44ca17a62b32a8dd1d89cd743532c8a96b262b164fd81b0c36 347e7709a0f5ace197beb6827f6cf04a31ff68ff2dff3707914c6b910658d00a
+lib/codeql/rust/elements/internal/generated/UseBoundGenericArgs.qll cedde7ccf689e3a2a246113be94544c206c56fb1c01b83b074e1f6edd3acfced f022ea4c653d1b5f311917efde8e59be27394ce7f6abf2561bb1e42f93f74adf
 lib/codeql/rust/elements/internal/generated/UseTree.qll 3d7cbcc8ae76068b8f660c7d5b81b05595026043015cd6b4d42a60ed4c165811 b9f0bcf82feb31f31406e787670fee93e1aa0966bcc0e4cc285c342e88793e4e
 lib/codeql/rust/elements/internal/generated/UseTreeList.qll 38efaa569b76ca79be047703279388e8f64583a126b98078fbbb6586e0c6eb56 1623a50fd2d3b1e4b85323ad73dd655172f7cbc658d3506aaa6b409e9ebe576e
 lib/codeql/rust/elements/internal/generated/Variant.qll fa6909715133049b3dba4622e6262fa30c4a9478b6219ec4fd12e07c58750709 71fc2ddac97fc4c4e6b92a13ee217cccc81dffc7c12295b6bc97c56ad25a92cc

rust/ql/lib/codeql/rust/elements/RetTypeRepr.qll

@@ -12,7 +12,7 @@ import codeql.rust.elements.TypeRepr
  *
  * For example:
  * ```rust
- * fn foo() -> i32 {}
+ * fn foo() -> i32 { 0 }
  * //       ^^^^^^
  * ```
  */

rust/ql/lib/codeql/rust/elements/UseBoundGenericArgs.qll

@@ -12,7 +12,7 @@ import codeql.rust.elements.UseBoundGenericArg
  *
  * For example:
  * ```rust
- * pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> {}
+ * pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> { 0 }
  * //                                                        ^^^^^^^^
  * ```
  */

rust/ql/lib/codeql/rust/elements/internal/RetTypeReprImpl.qll

@@ -17,7 +17,7 @@ module Impl {
    *
    * For example:
    * ```rust
-   * fn foo() -> i32 {}
+   * fn foo() -> i32 { 0 }
    * //       ^^^^^^
    * ```
    */

rust/ql/lib/codeql/rust/elements/internal/UseBoundGenericArgsImpl.qll

@@ -17,7 +17,7 @@ module Impl {
    *
    * For example:
    * ```rust
-   * pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> {}
+   * pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> { 0 }
    * //                                                        ^^^^^^^^
    * ```
    */

rust/ql/lib/codeql/rust/elements/internal/generated/Raw.qll

@@ -874,7 +874,7 @@ module Raw {
    *
    * For example:
    * ```rust
-   * fn foo() -> i32 {}
+   * fn foo() -> i32 { 0 }
    * //       ^^^^^^
    * ```
    */
@@ -1270,7 +1270,7 @@ module Raw {
    *
    * For example:
    * ```rust
-   * pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> {}
+   * pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> { 0 }
    * //                                                        ^^^^^^^^
    * ```
    */

rust/ql/lib/codeql/rust/elements/internal/generated/RetTypeRepr.qll

@@ -19,7 +19,7 @@ module Generated {
    *
    * For example:
    * ```rust
-   * fn foo() -> i32 {}
+   * fn foo() -> i32 { 0 }
    * //       ^^^^^^
    * ```
    * INTERNAL: Do not reference the `Generated::RetTypeRepr` class directly.

rust/ql/lib/codeql/rust/elements/internal/generated/UseBoundGenericArgs.qll

@@ -19,7 +19,7 @@ module Generated {
    *
    * For example:
    * ```rust
-   * pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> {}
+   * pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> { 0 }
    * //                                                        ^^^^^^^^
    * ```
    * INTERNAL: Do not reference the `Generated::UseBoundGenericArgs` class directly.

rust/ql/lib/codeql/rust/internal/TypeInference.qll

@@ -232,9 +232,14 @@ import M2
 module Consistency {
   import M2::Consistency
 
+  private Type inferCertainTypeAdj(AstNode n, TypePath path) {
+    result = CertainTypeInference::inferCertainType(n, path) and
+    not result = TNeverType()
+  }
+
   predicate nonUniqueCertainType(AstNode n, TypePath path, Type t) {
-    strictcount(CertainTypeInference::inferCertainType(n, path)) > 1 and
+    strictcount(inferCertainTypeAdj(n, path)) > 1 and
-    t = CertainTypeInference::inferCertainType(n, path) and
+    t = inferCertainTypeAdj(n, path) and
     // Suppress the inconsistency if `n` is a self parameter and the type
     // mention for the self type has multiple types for a path.
     not exists(ImplItemNode impl, TypePath selfTypePath |
@@ -278,7 +283,7 @@ private TypeMention getTypeAnnotation(AstNode n) {
   )
   or
   exists(Function f |
-    result = f.getRetType().getTypeRepr() and
+    result = getReturnTypeMention(f) and
     n = f.getFunctionBody()
   )
 }
@@ -291,6 +296,17 @@ private Type inferAnnotatedType(AstNode n, TypePath path) {
   result = n.(ShorthandSelfParameterMention).resolveTypeAt(path)
 }
 
+/**
+ * Holds if `me` is a call to the `panic!` macro.
+ *
+ * `panic!` needs special treatment, because it expands to a block expression
+ * that looks like it should have type `()` instead of the correct `!` type.
+ */
+pragma[nomagic]
+private predicate isPanicMacroCall(MacroExpr me) {
+  me.getMacroCall().resolveMacro().(MacroRules).getName().getText() = "panic"
+}
+
 /** Module for inferring certain type information. */
 module CertainTypeInference {
   pragma[nomagic]
@@ -436,14 +452,21 @@ module CertainTypeInference {
     result = inferTupleRootType(n) and
     path.isEmpty()
     or
-    result = inferAsyncBlockExprRootType(n) and
+    result = inferBlockExprType(n, path)
-    path.isEmpty()
     or
     result = inferArrayExprType(n) and
     path.isEmpty()
     or
     result = inferCastExprType(n, path)
     or
+    exprHasUnitType(n) and
+    path.isEmpty() and
+    result instanceof UnitType
+    or
+    isPanicMacroCall(n) and
+    path.isEmpty() and
+    result instanceof NeverType
+    or
     infersCertainTypeAt(n, path, result.getATypeParameter())
   }
 
@@ -580,7 +603,8 @@ private predicate typeEquality(AstNode n1, TypePath prefix1, AstNode n2, TypePat
       n2 = be.getRhs()
     )
     or
-    n1 = n2.(MacroExpr).getMacroCall().getMacroCallExpansion()
+    n1 = n2.(MacroExpr).getMacroCall().getMacroCallExpansion() and
+    not isPanicMacroCall(n2)
     or
     n1 = n2.(MacroPat).getMacroCall().getMacroCallExpansion()
     or
@@ -932,14 +956,17 @@ private predicate functionInfoBlanketLike(
  */
 bindingset[path, type]
 private predicate isComplexRootStripped(TypePath path, Type type) {
-  path.isEmpty() and
+  (
-  not validSelfType(type)
+    path.isEmpty() and
-  or
+    not validSelfType(type)
-  exists(TypeParameter tp |
+    or
-    complexSelfRoot(_, tp) and
+    exists(TypeParameter tp |
-    path = TypePath::singleton(tp) and
+      complexSelfRoot(_, tp) and
-    exists(type)
+      path = TypePath::singleton(tp) and
-  )
+      exists(type)
+    )
+  ) and
+  type != TNeverType()
 }
 
 /**
@@ -1541,7 +1568,8 @@ private module MethodResolution {
     MethodCall getMethodCall() { result = mc_ }
 
     Type getTypeAt(TypePath path) {
-      result = mc_.getACandidateReceiverTypeAtSubstituteLookupTraits(derefChain, borrow, path)
+      result = mc_.getACandidateReceiverTypeAtSubstituteLookupTraits(derefChain, borrow, path) and
+      not result = TNeverType()
     }
 
     pragma[nomagic]
@@ -1854,7 +1882,7 @@ private module MethodCallMatchingInput implements MatchingWithEnvironmentInputSi
     }
 
     private Type resolveRetType(TypePath path) {
-      result = this.getRetType().getTypeRepr().(TypeMention).resolveTypeAt(path)
+      result = getReturnTypeMention(this).resolveTypeAt(path)
     }
 
     pragma[nomagic]
@@ -2799,10 +2827,37 @@ private AssociatedTypeTypeParameter getFutureOutputTypeParameter() {
 }
 
 pragma[nomagic]
-private TraitType inferAsyncBlockExprRootType(AsyncBlockExpr abe) {
+predicate isUnitBlockExpr(BlockExpr be) {
+  not be.getStmtList().hasTailExpr() and
+  not be = any(Callable c).getBody() and
+  not be.hasLabel()
+}
+
+pragma[nomagic]
+private Type inferBlockExprType(BlockExpr be, TypePath path) {
   // `typeEquality` handles the non-root case
-  exists(abe) and
+  if be instanceof AsyncBlockExpr
-  result = getFutureTraitType()
+  then (
+    path.isEmpty() and
+    result = getFutureTraitType()
+    or
+    isUnitBlockExpr(be) and
+    path = TypePath::singleton(getFutureOutputTypeParameter()) and
+    result instanceof UnitType
+  ) else (
+    isUnitBlockExpr(be) and
+    path.isEmpty() and
+    result instanceof UnitType
+  )
+}
+
+pragma[nomagic]
+private predicate exprHasUnitType(Expr e) {
+  e = any(IfExpr ie | not ie.hasElse())
+  or
+  e instanceof WhileExpr
+  or
+  e instanceof ForExpr
 }
 
 final private class AwaitTarget extends Expr {

rust/ql/lib/codeql/rust/internal/TypeMention.qll

@@ -443,6 +443,34 @@ TypeMention getSelfParamTypeMention(SelfParam self) {
   result = self.getTypeRepr()
 }
 
+/**
+ * An element used to represent the implicit `()` return type of a function.
+ *
+ * Since the implicit type does not appear in the AST, we (somewhat arbitrarily)
+ * choose the name of the function as a type mention. This works because there
+ * is a one-to-one correspondence between a function and its name.
+ */
+class ShorthandReturnTypeMention extends TypeMention instanceof Name {
+  private Function f;
+
+  ShorthandReturnTypeMention() {
+    this = f.getName() and
+    not f.getRetType().hasTypeRepr()
+  }
+
+  override Type resolveTypeAt(TypePath typePath) {
+    typePath.isEmpty() and
+    result instanceof UnitType
+  }
+}
+
+pragma[nomagic]
+TypeMention getReturnTypeMention(Function f) {
+  result.(ShorthandReturnTypeMention) = f.getName()
+  or
+  result = f.getRetType().getTypeRepr()
+}
+
 class DynTraitTypeReprMention extends TypeMention instanceof DynTraitTypeRepr {
   private DynTraitType dynType;
 

rust/ql/lib/codeql/rust/internal/typeinference/BlanketImplementation.qll

@@ -90,7 +90,10 @@ module SatisfiesBlanketConstraint<
 
     Location getLocation() { result = at.getLocation() }
 
-    Type getTypeAt(TypePath path) { result = at.getTypeAt(blanketPath.appendInverse(path)) }
+    Type getTypeAt(TypePath path) {
+      result = at.getTypeAt(blanketPath.appendInverse(path)) and
+      not result = TNeverType()
+    }
 
     string toString() { result = at.toString() + " [blanket at " + blanketPath.toString() + "]" }
   }

rust/ql/lib/codeql/rust/internal/typeinference/FunctionType.qll

@@ -46,7 +46,7 @@ class FunctionPosition extends TFunctionPosition {
     result = f.getParam(this.asPosition()).getTypeRepr()
     or
     this.isReturn() and
-    result = f.getRetType().getTypeRepr()
+    result = getReturnTypeMention(f)
   }
 
   string toString() {
@@ -227,7 +227,10 @@ module ArgIsInstantiationOf<
   final private class ArgFinal = Arg;
 
   private class ArgSubst extends ArgFinal {
-    Type getTypeAt(TypePath path) { result = substituteLookupTraits(super.getTypeAt(path)) }
+    Type getTypeAt(TypePath path) {
+      result = substituteLookupTraits(super.getTypeAt(path)) and
+      not result = TNeverType()
+    }
   }
 
   private module IsInstantiationOfInput implements
@@ -332,10 +335,10 @@ module ArgsAreInstantiationsOf<ArgsAreInstantiationsOfInputSig Input> {
       CallAndPos cp, Input::Call call, FunctionPosition pos, int rnk, Function f,
       TypeAbstraction abs, AssocFunctionType constraint
     ) {
-      cp = MkCallAndPos(call, pos) and
+      cp = MkCallAndPos(call, pragma[only_bind_into](pos)) and
       call.hasTargetCand(abs, f) and
-      toCheckRanked(abs, f, pos, rnk) and
+      toCheckRanked(abs, f, pragma[only_bind_into](pos), rnk) and
-      Input::toCheck(abs, f, pos, constraint)
+      Input::toCheck(abs, f, pragma[only_bind_into](pos), constraint)
     }
 
     pragma[nomagic]

rust/ql/test/extractor-tests/generated/.generated_tests.list

@@ -75,7 +75,7 @@ MacroItems/gen_macro_items.rs c00f8045d9a7d6562da1d0136b335b685e2ec5dbd708763faa
 MacroPat/gen_macro_pat.rs 6bc63338397e6ef322a1824ce7d8fa68629a81c740f6e1d5347642501c83683a 6bc63338397e6ef322a1824ce7d8fa68629a81c740f6e1d5347642501c83683a
 MacroRules/gen_macro_rules.rs 5483484783b19a4f4cb7565cf63c517e61a76ce5b5b4bdc9b90f7e235a4c03b7 5483484783b19a4f4cb7565cf63c517e61a76ce5b5b4bdc9b90f7e235a4c03b7
 MacroTypeRepr/gen_macro_type_repr.rs cdb9670dde8b2a71256bc8d4acb1d63bd726cb49ee486ca2dbf1952884fd9c37 cdb9670dde8b2a71256bc8d4acb1d63bd726cb49ee486ca2dbf1952884fd9c37
-MatchArm/gen_match_arm.rs ac75b4836a103e2755bd47a1ee1b74af6eb8349adc4ebedaaa27b3ea3ae41aa5 ac75b4836a103e2755bd47a1ee1b74af6eb8349adc4ebedaaa27b3ea3ae41aa5
+MatchArm/gen_match_arm.rs 4f4e717930729b2161b9cf9cd5e2b86b8e919204f5f7d4993d2c4e1034858cea 4f4e717930729b2161b9cf9cd5e2b86b8e919204f5f7d4993d2c4e1034858cea
 MatchArmList/gen_match_arm_list.rs 6dcb92591c86771d2aeb762e4274d3e61a7d6c1a42da3dbace1cbc545b474080 6dcb92591c86771d2aeb762e4274d3e61a7d6c1a42da3dbace1cbc545b474080
 MatchExpr/gen_match_expr.rs 081c5d4c78cb71ccd13fb37a93d7f525267c51b179f44b5a22ca3297897002a0 081c5d4c78cb71ccd13fb37a93d7f525267c51b179f44b5a22ca3297897002a0
 MatchGuard/gen_match_guard.rs f0e84a1f608c0361983c516a40216cea149620a36e0aed7ff39b0b7d77a9ab8a f0e84a1f608c0361983c516a40216cea149620a36e0aed7ff39b0b7d77a9ab8a
@@ -106,7 +106,7 @@ RefPat/gen_ref_pat.rs aba7518649d9a37928e59a40d42f76cc0f4735e8daf711a3def6d2f052
 RefTypeRepr/gen_ref_type_repr.rs cf7b32d64550cd0b5033869b841089c1de292a1b25d3bd44c63ef9a265b9c8fb cf7b32d64550cd0b5033869b841089c1de292a1b25d3bd44c63ef9a265b9c8fb
 Rename/gen_rename.rs 05957dd5c7a0971223a485207ef3e98b0408a3e765cfb1fd6237bcc21c89f21a 05957dd5c7a0971223a485207ef3e98b0408a3e765cfb1fd6237bcc21c89f21a
 RestPat/gen_rest_pat.rs e9c977c8d3fce1d931abdfc025444e3e883468927f784ad1791670cace736aa7 e9c977c8d3fce1d931abdfc025444e3e883468927f784ad1791670cace736aa7
-RetTypeRepr/gen_ret_type_repr.rs 9db86003c7a4d91aa13fbc8220559bea6a05221c38c3f3ac0e03c6ac790aebcc 9db86003c7a4d91aa13fbc8220559bea6a05221c38c3f3ac0e03c6ac790aebcc
+RetTypeRepr/gen_ret_type_repr.rs b5d66327b445e8290be59a4fc4217d8163aa5ab5e49d9335efa1037b7ca5dc6f b5d66327b445e8290be59a4fc4217d8163aa5ab5e49d9335efa1037b7ca5dc6f
 ReturnExpr/gen_return_expr.rs 4f6ef29d7b3c60d6d71d1a6034a0721671f517428ba21897361a92b01009d38f 4f6ef29d7b3c60d6d71d1a6034a0721671f517428ba21897361a92b01009d38f
 ReturnTypeSyntax/gen_return_type_syntax.rs 648ce343023e7f80c445fada390870c5498add7fdf63dc82a800f6a77b7e7026 648ce343023e7f80c445fada390870c5498add7fdf63dc82a800f6a77b7e7026
 SelfParam/gen_self_param.rs 15491f86a32020c9ed3ecadc08c945ed01916b63683f95d2f5c1bedb4f3f01f2 15491f86a32020c9ed3ecadc08c945ed01916b63683f95d2f5c1bedb4f3f01f2
@@ -142,7 +142,7 @@ TypeParam/gen_type_param.rs 00b92ac7042ae83be1e37cd22f6d02098ca3157dc1ef45fbdf3b
 UnderscoreExpr/gen_underscore_expr.rs fe34e99d322bf86c0f5509c9b5fd6e1e8abbdf63dbe7e01687344a41e9aabe52 fe34e99d322bf86c0f5509c9b5fd6e1e8abbdf63dbe7e01687344a41e9aabe52
 Union/gen_union.rs 0adc276bf324661137b4de7c4522afd5f7b2776e913c4a6ecc580ce3d753a51d 0adc276bf324661137b4de7c4522afd5f7b2776e913c4a6ecc580ce3d753a51d
 Use/gen_use.rs 3a8a426109080ce2a0ed5a68a83cfa195196c9f0a14eff328b7be54d1131eede 3a8a426109080ce2a0ed5a68a83cfa195196c9f0a14eff328b7be54d1131eede
-UseBoundGenericArgs/gen_use_bound_generic_args.rs 1da801583b77f5f064d729a1d4313a863f1ad2e1dcc11c963194839cba977367 1da801583b77f5f064d729a1d4313a863f1ad2e1dcc11c963194839cba977367
+UseBoundGenericArgs/gen_use_bound_generic_args.rs 7b9542a4fd4025bdef5e3fab0e76a85c533936793d8791b5e4ed93d6d1e503e9 7b9542a4fd4025bdef5e3fab0e76a85c533936793d8791b5e4ed93d6d1e503e9
 UseTree/gen_use_tree.rs 90660192ec361e96d0fee9dc03c34fcdf0a102269df33be45856c63ad5d18ff2 90660192ec361e96d0fee9dc03c34fcdf0a102269df33be45856c63ad5d18ff2
 UseTreeList/gen_use_tree_list.rs 2494aadcec03a3f7a6e2ae448ee70ec6774f840e9519c668b2afe8cd968211c9 2494aadcec03a3f7a6e2ae448ee70ec6774f840e9519c668b2afe8cd968211c9
 Variant/gen_variant.rs fa3d3a9e3e0c3aa565b965fad9c3dc2ffd5a8d82963e3a55a9acbb0f14b603d6 fa3d3a9e3e0c3aa565b965fad9c3dc2ffd5a8d82963e3a55a9acbb0f14b603d6

rust/ql/test/extractor-tests/generated/MatchArm/gen_match_arm.rs

@@ -1,6 +1,6 @@
 // generated by codegen, do not edit
 
-fn test_match_arm(x: i32) -> i32 {
+fn test_match_arm(x: i32) {
     // A match arm. For example:
     match x {
         Option::Some(y) => y,

rust/ql/test/extractor-tests/generated/RetTypeRepr/gen_ret_type_repr.rs

@@ -4,6 +4,6 @@ fn test_ret_type_repr() -> () {
     // A return type in a function signature.
     // 
     // For example:
-    fn foo() -> i32 {}
+    fn foo() -> i32 { 0 }
     //       ^^^^^^
 }

rust/ql/test/extractor-tests/generated/UseBoundGenericArgs/gen_use_bound_generic_args.rs

@@ -4,6 +4,6 @@ fn test_use_bound_generic_args() -> () {
     // A use<..> bound to control which generic parameters are captured by an impl Trait return type.
     // 
     // For example:
-    pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> {}
+    pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> { 0 }
     //                                                        ^^^^^^^^
 }

rust/ql/test/library-tests/type-inference/CONSISTENCY/PathResolutionConsistency.expected

@@ -9,9 +9,9 @@ multipleCallTargets
 | main.rs:590:9:590:18 | ...::m(...) |
 | main.rs:591:9:591:20 | ... .m() |
 | main.rs:592:9:592:24 | ...::m(...) |
-| main.rs:2519:13:2519:31 | ...::from(...) |
+| main.rs:2524:13:2524:31 | ...::from(...) |
-| main.rs:2520:13:2520:31 | ...::from(...) |
+| main.rs:2525:13:2525:31 | ...::from(...) |
-| main.rs:2521:13:2521:31 | ...::from(...) |
+| main.rs:2526:13:2526:31 | ...::from(...) |
-| main.rs:2527:13:2527:31 | ...::from(...) |
+| main.rs:2532:13:2532:31 | ...::from(...) |
-| main.rs:2528:13:2528:31 | ...::from(...) |
+| main.rs:2533:13:2533:31 | ...::from(...) |
-| main.rs:2529:13:2529:31 | ...::from(...) |
+| main.rs:2534:13:2534:31 | ...::from(...) |

rust/ql/test/library-tests/type-inference/main.rs

@@ -2122,6 +2122,10 @@ mod async_ {
         async { S1 }
     }
 
+    fn f3() -> impl Future<Output = ()> {
+        async {}
+    }
+
     struct S2;
 
     impl Future for S2 {
@@ -2135,14 +2139,15 @@ mod async_ {
         }
     }
 
-    fn f3() -> impl Future<Output = S1> {
+    fn f4() -> impl Future<Output = S1> {
         S2
     }
 
     pub async fn f() {
         f1().await.f(); // $ target=S1f target=f1
         f2().await.f(); // $ target=S1f target=f2
-        f3().await.f(); // $ target=S1f target=f3
+        f3().await; // $ target=f3
+        f4().await.f(); // $ target=S1f target=f4
         S2.await.f(); // $ target=S1f
         let b = async { S1 };
         b.await.f(); // $ target=S1f
@@ -2824,6 +2829,52 @@ mod if_expr {
     }
 }
 
+mod local_function {
+    pub fn f() -> () {
+        fn local(x: i32) -> i32 {
+            x + 1 // $ target=add
+        }
+    }
+}
+
+mod block_types {
+    #[rustfmt::skip]
+    fn f1(cond: bool) -> i32 {
+        // Block that evaluates to unit
+        let a = { // $ type=a:()
+            if cond {
+                return 12;
+            }
+        };
+        0
+    }
+
+    #[rustfmt::skip]
+    fn f2() -> i32 {
+        // Block that does not evaluate to unit
+        let b = 'label: { // $ MISSING: b:i32
+            break 'label 12;
+        };
+        println!("b: {:?}", b);
+        0
+    }
+
+    fn f3() -> i32 {
+        return 0;
+    } // should only have type `i32`, not `()`
+
+    #[rustfmt::skip]
+    fn f4(cond: bool) -> i32 {
+        let a = { // $ certainType=a:()
+            if cond {
+                return 12;
+            };
+        };
+        println!("a: {:?}", a);
+        0
+    }
+}
+
 mod blanket_impl;
 mod closure;
 mod dereference;
@@ -2863,4 +2914,5 @@ fn main() {
     pattern_matching_experimental::box_patterns(); // $ target=box_patterns
     dyn_type::test(); // $ target=test
     if_expr::f(true); // $ target=f
+    local_function::f(); // $ target=f
 }

rust/schema/annotations.py

@@ -266,7 +266,7 @@ class _:
 
 
 @annotate(MatchArm)
-@rust.doc_test_signature("(x: i32) -> i32")
+@rust.doc_test_signature("(x: i32)")
 class _:
     """
     A match arm. For example:
@@ -1738,7 +1738,7 @@ class _:
 
     For example:
     ```rust
-    fn foo() -> i32 {}
+    fn foo() -> i32 { 0 }
     //       ^^^^^^
     ```
     """
@@ -2466,7 +2466,7 @@ class _:
 
     For example:
     ```rust
-    pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> {}
+    pub fn hello<'a, T, const N: usize>() -> impl Sized + use<'a, T, N> { 0 }
     //                                                        ^^^^^^^^
     ```
     """