Rust: implement Expr::getType for cases where rust-analyzer does not provide one

Author: aibaars

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

@@ -11,6 +11,7 @@ private import codeql.rust.elements.internal.generated.Synth
 private import codeql.rust.elements.Format
 private import codeql.rust.elements.NamedFormatArgument
 private import codeql.Locations
+private import codeql.rust.elements.Variable
 
 /**
  * INTERNAL: This module contains the customizable definition of `FormatTemplateVariableAccess` and should not
@@ -36,5 +37,9 @@ module Impl {
 
     /** Gets the underlying `NamedFormatArgument` . */
     NamedFormatArgument getArgument() { result = argument }
+
+    override string getType() {
+      result = any(Variable v | v.getAnAccess() = this).getPat().getType()
+    }
   }
 }

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

@@ -5,6 +5,8 @@
  */
 
 private import codeql.rust.elements.internal.generated.LiteralExpr
+private import codeql.rust.elements.FormatArgsExpr
+private import codeql.rust.elements.LiteralPat
 
 /**
  * INTERNAL: This module contains the customizable definition of `LiteralExpr` and should not
@@ -27,5 +29,13 @@ module Impl {
    */
   class LiteralExpr extends Generated::LiteralExpr {
     override string toString() { result = this.getTextValue() }
+
+    override string getType() {
+      result = super.getType()
+      or
+      exists(FormatArgsExpr f | f.getTemplate() = this and result = "&str")
+      or
+      result = any(LiteralPat p | p.getLiteral() = this).getType()
+    }
   }
 }

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

@@ -5,6 +5,7 @@
  */
 
 private import codeql.rust.elements.internal.generated.PathExpr
+private import codeql.rust.elements.CallExpr
 
 /**
  * INTERNAL: This module contains the customizable definition of `PathExpr` and should not
@@ -23,5 +24,22 @@ module Impl {
    */
   class PathExpr extends Generated::PathExpr {
     override string toString() { result = this.getPath().toString() }
+
+    override string getType() {
+      result = super.getType()
+      or
+      // Special case for `rustc_box`; these get translated to `box X` in the HIR layer.
+      // ```rust
+      // #[rustc_box]
+      // alloc.boxed::Box::new(X)
+      // ```
+      not exists(super.getType()) and
+      exists(CallExpr c, string tp |
+        c.getAnAttr().getMeta().getPath().getPart().getNameRef().getText() = "rustc_box" and
+        this = c.getExpr() and
+        tp = c.getArgList().getArg(0).getType() and
+        result = "fn new<T>(T) -> Box<T, Global>".replaceAll("T", tp)
+      )
+    }
   }
 }