Rust: Implement type inference for ArrayRepeatExprs.

Author: geoffw0

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

@@ -1181,9 +1181,17 @@ private Type inferIndexExprType(IndexExpr ie, TypePath path) {
 }
 
 pragma[nomagic]
-private Type inferArrayListExprType(/*ArrayExpr*/ArrayListExpr ale, TypePath path) {
+private Type inferArrayExprType(ArrayExpr ae, TypePath path) {
+  // an array list expression (`[1, 2, 3]`) has the type of the first (any) element
   exists(Type type0, TypePath path0 |
-    type0 = inferType(ale.getExpr(0), path0) and
+    type0 = inferType(ae.(ArrayListExpr).getExpr(0), path0) and
+    result = type0 and
+    path = TypePath::cons(any(ArrayTypeParameter tp), path0)
+  )
+  or
+  // an array repeat expression (`[1; 3]`) has the type of the repeat operand
+  exists(Type type0, TypePath path0 |
+    type0 = inferType(ae.(ArrayRepeatExpr).getRepeatOperand(), path0) and
     result = type0 and
     path = TypePath::cons(any(ArrayTypeParameter tp), path0)
   )
@@ -1565,7 +1573,7 @@ private module Cached {
     or
     result = inferIndexExprType(n, path)
     or
-    result = inferArrayListExprType(n, path)
+    result = inferArrayExprType(n, path)
     or
     result = inferForLoopExprType(n, path)
   }

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

@@ -1830,7 +1830,7 @@ mod loops {
         for u in vals1 { } // $ type=u:u8
 
         let vals2 = [1u16; 3]; // $ MISSING: type=vals2:[u16; 3]
-        for u in vals2 { } // $ MISSING: type=u:u16
+        for u in vals2 { } // $ type=u:u16
 
         let vals3: [u32; 3] = [1, 2, 3]; // $ MISSING: type=vals3:[u32; 3]
         for u in vals3 { } // $ type=u:u32

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

@@ -2639,8 +2639,12 @@ inferType
 | main.rs:1829:30:1829:30 | 3 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:1830:13:1830:13 | u |  | {EXTERNAL LOCATION} | u8 |
 | main.rs:1830:18:1830:22 | vals1 | [T;...] | {EXTERNAL LOCATION} | u8 |
+| main.rs:1832:13:1832:17 | vals2 | [T;...] | {EXTERNAL LOCATION} | u16 |
+| main.rs:1832:21:1832:29 | [1u16; 3] | [T;...] | {EXTERNAL LOCATION} | u16 |
 | main.rs:1832:22:1832:25 | 1u16 |  | {EXTERNAL LOCATION} | u16 |
 | main.rs:1832:28:1832:28 | 3 |  | {EXTERNAL LOCATION} | i32 |
+| main.rs:1833:13:1833:13 | u |  | {EXTERNAL LOCATION} | u16 |
+| main.rs:1833:18:1833:22 | vals2 | [T;...] | {EXTERNAL LOCATION} | u16 |
 | main.rs:1835:13:1835:17 | vals3 |  | file://:0:0:0:0 | [] |
 | main.rs:1835:13:1835:17 | vals3 | [T;...] | {EXTERNAL LOCATION} | i32 |
 | main.rs:1835:13:1835:17 | vals3 | [T;...] | {EXTERNAL LOCATION} | u32 |
@@ -2657,14 +2661,18 @@ inferType
 | main.rs:1836:18:1836:22 | vals3 | [T;...] | {EXTERNAL LOCATION} | i32 |
 | main.rs:1836:18:1836:22 | vals3 | [T;...] | {EXTERNAL LOCATION} | u32 |
 | main.rs:1838:13:1838:17 | vals4 |  | file://:0:0:0:0 | [] |
+| main.rs:1838:13:1838:17 | vals4 | [T;...] | {EXTERNAL LOCATION} | i32 |
 | main.rs:1838:13:1838:17 | vals4 | [T;...] | {EXTERNAL LOCATION} | u64 |
 | main.rs:1838:26:1838:26 | 3 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:1838:31:1838:36 | [1; 3] |  | file://:0:0:0:0 | [] |
+| main.rs:1838:31:1838:36 | [1; 3] | [T;...] | {EXTERNAL LOCATION} | i32 |
 | main.rs:1838:31:1838:36 | [1; 3] | [T;...] | {EXTERNAL LOCATION} | u64 |
 | main.rs:1838:32:1838:32 | 1 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:1838:35:1838:35 | 3 |  | {EXTERNAL LOCATION} | i32 |
+| main.rs:1839:13:1839:13 | u |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:1839:13:1839:13 | u |  | {EXTERNAL LOCATION} | u64 |
 | main.rs:1839:18:1839:22 | vals4 |  | file://:0:0:0:0 | [] |
+| main.rs:1839:18:1839:22 | vals4 | [T;...] | {EXTERNAL LOCATION} | i32 |
 | main.rs:1839:18:1839:22 | vals4 | [T;...] | {EXTERNAL LOCATION} | u64 |
 | main.rs:1841:13:1841:24 | mut strings1 | [T;...] | {EXTERNAL LOCATION} | str |
 | main.rs:1841:28:1841:48 | [...] | [T;...] | {EXTERNAL LOCATION} | str |